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White Rot and the Quarantine Zone

It’s garlic harvesting season in the northern hemisphere, so recently while helping out with the harvest at a local farm, I had the chance to learn about a challenge involving growing garlic in southern Idaho. The challenge stems from a disease called white rot. It’s caused by a fungus (Sclerotium cepivorum), and it affects all alliums, including garlic, onions, chives, and ornamental alliums. This disease causes the leaves of alliums to die back, their bulbs to decay, and their roots to rot, ultimately turning the plants to mush. Sclerotia, the dormant stage of the fungus, are small (about the size of a poppy seed), black, spherical structures that can survive in soil for more than 20 years. They remain dormant until the exudates of allium plants awaken them, at which point they begin to grow, unleashing their destruction. Sclerotia can be moved around by farm equipment, flood and irrigation water, wind, and by attaching themselves to plant material. Once this fungus has established itself in a field, it is extremely difficult to eradicate, making the field virtually unfit for allium crops.

The threat of white rot and the monetary damage that it can cause led to the establishment of a quarantine zone in southern Idaho in order to protect its $55 million dollar a year onion industry. Due to the quarantine zone, all garlic that is grown for seed within the zone must be inspected and certified, and any garlic seed (i.e. garlic cloves) that are brought into the zone must go through a rigorous testing process in order to be certain it is free of the white rot pathogen before it can be planted. Garlic is a specific threat, because while onions in the zone are typically grown from seed and so are largely free from harboring sclerotia, garlic is grown from cloves, which can readily carry sclerotia. This process significantly limits the amount and the variety of garlic that can be grown in the quarantine zone. While the quarantine is essential for warding off the threat of this particular pathogen, it stifles the garlic growing industry and makes it difficult for new garlic growers to establish themselves.

Growing garlic is already an incredibly challenging pursuit due to the amount of time and physical labor that goes into planting, harvesting, drying, grading, etc. The quarantine, while understandable, is yet another added challenge. Learn more about this issue by reading this article found at Northwest Food News.